Transmission line



I March 1, 1932. 0, s'n 1,848,071

' TRANSMISSION LINE Original Filed May 27, 1927 s Sheets-Sheet 1 Imvzivrok By M QM M ml I ATTORNEES- March 1, A Q AUSTlN TRANSMISSION LINEOriginal Filed May 27. 1927 6 Sheets-Sheet 2 E as Fig.5

INVFNTOR BY Man I W ATTORNEYJ March 1, 1932. A. o. AUSTIN 1,848,071

' TRANSMISSION LINE Original Filed May 27. 1927 6 Sheets-Sheet I5 IN VENTOR 4? M I. M ATTORNEYS March 1, 1932. AIO AUSTIN TRANSMISSION Lima:

Original Filed May 27. 1927 6 Sheets-Sheet 4 INVENTOR mL/JM maul/,

ATTORNEYS Mara A. O AUSTIN.

TRANSMISSION LINE 6 Sheets-Sheet 5 Original Filed May 27, 1927 INVENTOR4.

lTTORNEYS March 1, 1932. A. o. AUSTIN 1,848,071

TRANSMISSION LINE 'Original Filed May 27, 1927 6 Sheets-Sheet 6 NRQ Q\.R R

Patented Mar. 1, 1932 UNITED STATES PATENT OFFICE- f ARTHUR. O. AUSTIN,OF NEAR BARBERTON, OHIO, ASSIGNOR, BY MESN'E ASSIGNMENTS,

TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF JERSEY vTRANSMISSIOK LINE Application filed May 27, 1927, Serial No. 194,607.Renewed Eanuary 14,1982.

This invention relates to high potential transmission lines and has forone object the provision of means for keeping down voltages induced inthis transmission conductor by external disturbances and also forraising the voltage at which flash-over to ground will occur. Otherobjects and advantages will appear from the following' descriition andclaims. The invention is exempli ed in the combination and arrangementof parts shown in the accompanying drawings and described in thefollowing specification and it is more particularly pointed out in theappended claims.

In the drawings:

Fig. 1 is an elevation of a conductor support illustrating oneembodiment of the present invention.

Fig. 9. is an elevation at right angles to Fig. 1.

Figs. 3 and 4 are views similar to Figs. 1 and 2 respectively butshowing the invention applied to a skeleton tower construction.

Fig. 5 is a diagrammatic figure showing different connections betweenthe charging or counter potential wire and ground.

Figs. 6 and 7 are views similar to Figs. 1 and showing anotherembodiment of the invention.

Figs. 8, 9, and 10 are elevations of other forms of the invention.

Fig. 11 is an end elevation of the structure shown in Fig. 10.

Fig. 12 is an elevation showing anothe arrangement.

The economical construction of transmission lines where reliability isan important consideration is exceedingly difficult where the linestraverse av district subject to lightning or where a high transientpotential is likely to be induced upon the conductors. Lightning mayeasily set up stresses which would cause flash-over of even exceedinglylarge insulators. Large. insulators in turn require greater towerclearances. and the greater tower clearam-e in turn tends to increasethe ineclmniral stresses imposed bythe conductors and greatly increasesthe cost of the supporting -"Ql'll(ii'lll$i. The increased clearancebetween conductors while tending to reduce the corona voltage, increasesthe line react-ance and tends to increasethe cost of the system as awhole forv a given amount of power transmitted.

In my improved line construction, the conditions are greatlyimprovedwhich will result in material reduction, if not the completeelimination of flash-overs or arcs from conductor to ground on manysystems. The improved construction is particularly applicable to newlinesand may be applied to many old lines at comparatively slightadditional expense. The invention permits of a much closer spacing ofconductors than is possible in constructions Where all dependence mustbe placed on the insulator itself for providing resistance toflash-over. This closer spacing has many economic advantages resultingin supporting structures of lower cost and better regulation on theline, and since the spacing of the conductors may be reduced, themaximum height of the conductor supports and consequently induced voltage due to atmospheric changes may be kept down, particularly formultiple circuit towers.

In transmission operation the voltageinduced by lightning is usually thedetermining factor in causing flash-overs as the induced voltage islikely to be many times the flashover the insulator will carry. By farthe greatest number of exceedingly high voltages produced on the lineare caused by the release of a bound charge in the line which occurswhere a charged cloud over or near the transmission line discharges toground or to an adjacent cloud. For mechanical and electrical reasonsand in order to provide safe clearances. it is necessary to installtransmission conductors at some distance above the ground. WVhere theclearance between conductors remains the same, the charge in; duced upona conductor by a charged cloud will tend to increase approximately asthe height of the conductor above the earths surface. The closer theconductors are together, the less will be the bound charge on each,other conditions being the same. Upon the release of a bound charge thevoltage will rise l tential is directly proportional to the charge andinversely proportional to the electrostatic capacity. In order to keepthe induced voltage or potential as low as possible, it is notgonlyadvisable to keep down the bound charge, but it is equally important toincrease theelt'ect'ive electrostatic capacity of the conductor toaround or to objects of lower potential..,,I ly keeping the rise inpotential down, it may be possible to prevent a discharge from-conductorto ground over the insulator or from conductor to the supportingstructure. -It is evident that the above applies equally well to whethera positive or negative charge is released on the conductor.

The amount of energy which can be stored in a condenser increases as thesquare of the potential or voltage. It is therefpre important that ahigh voltage be used if possible where considerable energy is to bestored. \Vhere a high voltage or potential can be impressed upon theconductor, brush discharge will increase its efiective size and capacityto ground or conductors of lower potential and also tend to dissipatethe charge. Many transmission lines equipped with ground or static wirescannot make use of a high voltage between the conductors and ground orstatic wire owing to the fact that flasiroven to ground Will limit thestored energy. Raising the dashing potential between conductor andground will make it possible to store more energy and thereby reduce thepossibility of.

an interruption due to flash-over.

In my improved transmission line it is possible tr. place very' muchhigher potentials upon the conductors and thereby take advantage of thelargest amount of energy which may. be stored without causing flash-overfrom conductors to ground. Since it is not necessaryto provide all theinsulation in the insulator itself. the conductors may be brought nearerogether. This. as stated above, tends to reduce the bound charge on anyindividual conductor, makes it possible to operate some of theconductors at a lower height. which, in turn. tends to keep down thebound charge and. in addition. the lower height of the conductors meansgreater eiicc tive capacity to ground. all'of which tends to keep downthe maximum induced potentiul. These advantages. as well as theelimination of flaslrovcrs on existing lines. better regulation, lowercost of structures and narrower rights of way, all make the improvedconstruction of great economic importance.

There are several methods of carrying out the principles of theinvention which, while appearing different upon the surface, are ineiiect the same as to essentials.

In the construction shown in Figs. 1 and 2, the power conductors 10 aresupported on insulators 11, which, in turn, are mounted on cross arms 12and 13. The cross arms 12 and 13 are mounted on a wood pole 14. Inaddition to the power conductors, a conductor 15, which I shall call acharging or counter potential wire. is mounted on a bayonet 16. Thisconductor 15 may be at. above. or below the level of the powerconductors l0 depending upon the electrical conditions which it isdesired to set up. The conductor 15 is preferably tied into the metalbraces 17 and bolts 18 connecting the insulator pins to the braces, tolead '19. and to the gap members 20. The conductor 15 is connected toground through a high resistance or a rcactunce connected to earth atvarious points along the line. In general, however. the conductor if)need have no direct ground connection on many sys tems, its potentialbeing established by leakage over the supporting structure. One methodis to connect the charging or counter potential wire 15 to groundthrough a circuit breaker or reactance at. the end of the line. In casean arc picks up between the line conductor and the metal supporting workelectrically connected to the conductor 15, the arc may be interruptedthrough the functioning of the rciu'ztancc as in the case of a Petersoncoil or by the opening of the circuit breaker. A suitable circuitbreaker or fuse maybe effective in clearing the are on shorter lineswhere the charging current not too high. This type of construction lendsitself to another method of treatmcnt of eliminating an are betweenconductor and supporting structure tied into the charging wire such asthe Nicholson arcing ground supprcsscr where the conductor and chargingwire would be electrically tied together by suitable means momentarilyand then opened through a circuit breaker. Establishing the samepotential, between conductor and charging wire will eliminate the arewhich could then be opened by the circuit breaker.

In very long lines it may be preferable to break up the line intosections in order that the charging current between conductor 15 and thepower conductors be so reduced that the arc n'iay be readily opened by acircuit breaker or a system of fuses shown in Fig. Any suit-able form oftrue or magazine oi fuses may be substituted tor the circuit breaker iidesired. here multiple fuses are used. it is desirable to inserta gap inall fuses otherthan the first one connected to the line. This permits otthe clearing of the line and the utilization of the other fuses wheredischarges occur in rapid succession, as in this case it may beimpossible to replace the first fuse before a second discharge takesplace. The charging current between conductor and charging wire 15 maybe utilized for clearing the are as in the case of the Peterson coil.The charging wire 15 permits carrying of! any'unbalanced leakage orcharging current so that the burning of the structure will be preventeddue to the leakage of current at normal frequency. The burning of thestructure will also be prevented in case of the flashover of theinsulator where the charging conductor is connected to ground.

In operation the charging or counter potential wire may be regarded asperforming two distinct electrostatic functions. Owing to its relativeposition and due to the effect it will have on ground potential due toleakage to ground or its connection at the end of the line, it will tendto reduce the bound charge on the power conductors 10. Upon thedischarge of a cloud, the bound charge will produce a rise in potentialnot only in conductors 10, but also in the charging conductor 15. Sincethe bound charge released upon the conductor and upon the charging Wireis of the same potential, the charge released on the charging wire willtend to raise the potential of the supporting structure electricallyconnected to this charging wire and insulated from ground. This rise inpotential of the supporting structure adjacent to the insulatorssupporting the power conductors will reduce the momentarily inducedvoltage upon the insulators by an amount equal to the rise in potentialof the supporting structure charged by the counter potential wire. Theamount of this rise in potential will depend upon the charge on theconducting wire and upon the ell'ective capacity of this conductor andsupporting structure to ground. The amount of the charge may becontrolled by the height, size, or lo cation of the charging wire orell'ective ca- ..pacity of the insulated section of the supportingstructure to ground. In order that the charge on the conductor 15 may beutilized to raise the potential of the supporting structure. it isnecessary that the charge be prevented from flowing to ground over thepole. In order that this maybe accomplished, an ungrounded section ofthe pole is utilized below the lowest conducting support. In case ofexcessively high stresses set up, it

may be impossible to prevent a discharge over this section and in orderto prevent burning or shattering of the pole. a screen or shielding typeof discharge gap permits discharge to points 20 and 21 and then throughthe fuse 24 or points 92 and 23 it the fuse is blown. A single gap or aseries of gaps may be utilized depending upon conditions and resultsdesired. \Vliere a series of gaps is used, one or more of the gaps maybe will blow thefuse, which. in general, will clear the line of theground.

Where wood structures are used, much effective insulation may be'provided between the portion charged by the charging or counterpotential wire 15. so that great care in the location of the chargingwire is not necessary. Where the insulating zone of the supportingstructure is restricted, however, it is essential that the charging wirebe so located that the insulation of the insulator supporting theconductors be effectively utilized as well as the drop in potentialacross the insulating section. An example in this connection willillustrate the application. An insulator having an effective flash-overunder the release of a bound charge of 9.00 K. V. will provide ,aflashing potential of only 200 K. V. when mounted on a groundedstructure. If an ordinary ground wire is used which reduces theeffective potential 40%, the field set up by the cloud may be increased66 70 before reaching 200 K. V. on the insulator, or, in other words,the effect of the ground wire as compared to the line without the groundwire would be to increase the flashing potential of the insulator from200 K. V. to 333 K. V. If. however, a section of the pole is utilizedwhich is equivalent to a flashing potential of 600 K. V., a very higheitective insulation may be obtained to withstand the released charge.If the charging wire is so placed that the (500 K. V. effectiveinsulation of the supporting structure is utilized at the same time asthe 200 K. V. flashing potential of the insulator, a total effectiveinsulation or flash-over of 800 K. V., the sum of the two, will result.If, however, the coun ter potential wire is so located that thepotential of the supporting structure will be raised to the samepotential as the power conductor, there would be no abnormal potentialacross the insulator and the total flash-over of the two would bereduced by the amount of potential which could be carried by the insulator or the resulting effective flash-over of the structure will be600 K. V. in place of 800 K. V. If the charging conductor reaches thepotential of the supporting structure so that the difl erence inpotential between the supporting structure and the power conductorwillexceed the flash-over potential of the insulator. a discharge willtake place between the two. It is therefore important that the potentialof the supporting structure be such that the difference in potentialbetween the supporting structure and the power con ductor does notexceed the flashing potential of the insulator to obtain the bestresults. It is evident where the counter potential wire can be utilizedto control the potential of Y the supporting structure immediatelyadlightning may jacent the insulators all stress induced by v becounteracted so that the tendency of the insulator to flash under thesurge will'be negligible providing sufiicient insulation can befurnished by the supporting structure. I

\Vhere extreme conditions are encountered,

this potential may be added to that of the insulator, greatly increasingthe effective fiash over between conductor and ground. Since th'e'stored energy will increase as the 'square' of thevoltageor potential, theincrease in potential of the conductors above ground before flashingwill permit of the momentary storing of the released charge which mightotherwise cause flash-over. This along the line and is a charge isreadily dissiaated as it goes out bsorbed by the losses and capacity sothat it is necessary to pro vide foflra'n excessively high potential fori "an exceedingly short space of time only, un-

der which conditions, wood and many other" materials'may act aseffective insulators, providing suitableinsulators are provided whichwill Withstand continuous normal frequency potential.

It is possible to so construct the charging conductor that the chargewill flow away at approximately the same rate on this concuctor as thaton the power conductors .so that the relative difference in potentialover the insulator and between the insulated section and ground will beapproximately the same until the potential is reduced to a point wherethere 'is no danger of the flashing of the insulator. Since theattcnuationof the voltage isvcr rapid where the charge travels away fromthe point of maximum potential, great care in providing a carefulrelation is not essential to successful operation. Since the potentialof the conductors insulated from the ground will be determined by theirrclative electrostatic capacity to ground and the charge upon them, afurther reduction in potential may be effected by bringing a conductorwith a ground potential near the trans-- mission conductors. This,however, should not be accomplished at the expense of lowering theflash-over voltage between conductor and ground. Otherwise, the dangerof flash over may actually be increased rather than reduced.

One method of accomplishing this is to use an insulated ground wiremounted on an insulator 26 and connected to ground through a lead 27.The insulation furnished by the arm 13 and the insulator 26 should beequivalent to the insulated zone of the supporting structure to developthe full possibilities of the charging wire 15. Since there is: nonormal voltage arcing across insulator 3 3, this insulator may bemounted on a wood pin of good length if so desired to .l'urther increasethe lash-over of the combination. (inc nieth- 0d of attaching the groundto conductor is to attach a jumper 27 at some distance out on thetransmission conductor bringing the umper down at an angle to the poleand attachmg it near the base of same. This jump er or down lead shouldbe carried to ground in such away that it will not eliminate theinsulation of the pole. The ground wire 25 tends to function similarlyto the usual ground wire with the exception that the insulation of thepole is not eliminated, and, since a much higher potential may existbetween the conductors and ground wire before flash-over will occur, thestored energy can be greatly increased over the usual application of theground wire. \Vith the increase in potential on the conductor. brushdischarges occur which increase the ciiective electrostatic capacity anddissipate the charge so that it is highly advantageous to raise theflashing potential between conductor and ground, even though a groundconductor is used for absorption, as it increases the effectiveness ofthis conductor.

Figs. 3 and 4 show an application of the improved method of constructionapplied to a steel tower. In order to provide an insulating sectionbetween the conductor supports and ground, an insulating section 30replaces a steel section of the tower. The ends of this section may beprovided with discharge horns 31 which tend to shield the wood orinsulating members and also tend to keep an are free of the insulatingmembers should an unusually heavy discharge of lightning cause an arc toground across the discharge members 3i. These members, it properlyapplied, prevent the shattering of the insulating members due to anabnormally high stress, even though a discharge takes place between themembers. An additional charging wire may he placed lower down on thetower as at 32. A tower may be charged by one or more wires or infavorable cases by the release of a bound charge on the tower itself.The charging wire extending over a considerable section of the line,however, has the advantage in that it may be used to facilitateoperation of relays used in clearing the line and to prevent burning ofthe members of the insulated zone 30 or the insulating sections shown inother types of construction.

The charging wire 15 may be provided with a circuit breaker which willclear the line in case an arc occurs between conductors and theinsulated section. The circuit breaker may be replaced by a magazinefuse attached if so desired as in Fig. 5. One or all of the fusearrangements maybe used in place of the circuit breaker 33 or fordifferent sections of the line. The high tension Fuse 3-1 is shown inseries with a resistance 35 which latter has a shunting gap 86, thelower end being connected to ground.

It sections of the charging wire 15 are left out periodically to reducethe amount of charging current in. case of an are between conductor andtower top, it is evident that a circuit breaker or a fuse at the end'ofthe line may not function, as the charging current will maintain theare, even though a circuit breaker or fuse operates. If, however, thecombination fuse 34 and resistance 35 is used to connect variousinsulated sections to ground, the conditions will be the same as wherethe charging conductor is continuous except in the case of relayoperation. The smaller amount of charging current with the shortersections of line connected by the charging wire may be cleared of an arebetween conductor, and the insulated section by the operation of thefuse, as the charging current of the smaller section may not besufficient to maintain an are once the fuse is blown. Several fuses maybe used to form multiple paths in case discharges occur before fuse 34can be replaced. Fuses 37 and 38 are such fuses and come into operationwhen the aps 39 and 40 are arced by a high voltage. ince the gaps usedin series with the fuses are of different lengths, the shorter one willtake a discharge and protect the other ones. After the fuse connected tothis gap has cleared the line, the fuse having the next larger gap willtake the next discharge sufiicient to are to ground. These fuses may belocated at the end of the line, at each section, or at individualstructures as desired. When located at individual structures, the gapand fuse must of necessity bridge the insulating section of thestructure to work effectively.

Where the charging conductor 15 or 33 is not used, the resistance 35should-be relatively high at the tower so that the potential of theinsulated section of the tower will rise together with the conductorupon the release of a bound charge and not escape too quickly throughthe resistance. This resistance may run from several thousands ohms toseveral hundred thousands ohms and still prevent burning of theinsulated section due to unbalanced currents. The resistance may be inany suitable form, preferably one which needs little care and attentionand one which willhave a long life under operating conditions.Insulating rods of graphite, carborundum, or any suitable combination ofweather protecting tubes packed with a resistance com osition or filledwith a high resistance fiui. may be used for the purpose. The resistancemembers should preferably be long enough so that they will not flashover at an unnecessarily low voltage and they should also be such thatthey will not bereadily destroyed, although they can still be effective,even though they would be destroyed by a single discharge, as dischargesseldom occur twice in succession at the same point, except afterconsiderable interval'of time which would permit replacing a damagedmember.

Fig. 6 shows another form of the improved construction of which Fig. 7is a side elevation. In Figs. 6' and 7 one of the insulators providinginsulation for the ground or earth wire25is shown as an ordinarysuspension insulator 26 and the insulator is made of a. piece of wood orfibre 41 in the other case. These insulators should be of suitablelength in order to provide suflicient insulation to prevent flashingover the insulating zone between their point of support and ground. Theconstruction in Figs. 6 and 7 shows the insulators mounted on wood crossarms 42. The insulator supports are connected electrically to thecharging wires 15 by jumpers 43. In some cases these members may be usedfor suitable tension members for increasing the strength of the crossarm. In favorable cases they may be omitted entirely. This isparticularly true where the cross arms are made of steel, as no bondingis necessary. The insulated section may be protected from shattering byhorns or screens 31 and from burning by resistance members 42 and a fuse.43, as previously described. This method of protection is applicablewhere the charging wire 15 is eliminated or is not carried to groundthrough its own resistance or reactance at the end of the line. Wherethe resistance 42 is high and it is not necessary to develop anexceedingly high potential in a supporting structure, the upperinsulating zone may be jumpered by a. conductor 44. The resistance 42must of necessity be high in this case, otherwise the charge will flowto ground and the full induced potential between conductor and groundmust be carried by the insulator following the release of a boundcharge. Should a discharge take place followed by a power arc, the fuse43 will usually clear the line and restore normal operation. This methodof protection is particularly applicable where the line is broken upinto sections in order to keep down the charging current betweenconductor and charging wires 15 so that the are may be cleared uponinterruption of the path to ground by the blowing of the fuse 43 or theopening of a circuit breaker if placed between the charging wire 15 andground as shown in Fig. 4.

Fig. 8 shows another form of the invention in which the supportingstructure ma have wood or steel members 50. Thesemembers may be selfsupporting or guyed by members 51. The power conductors 52 are supportedfrom insulators 53, which in turn are hung from a member 54. This member54 is preferably of steel and is equipped with charging wires 55 aspreviously described. The member 54 is suspended by insulators 56 whichare protected by discharge members 57. If desired, ground or earth wiresmay be mountidlStllI'bllIlCGS.

tend torprevent the burning of the wood mem- ,bGlS 56. lZVhere it isdesired to reduce the potential on the conductors so as to provide afurther factor of safety, ground wires 58 and 59 may be installed. Theseare connected to ground through the guys 51. This areran ement permitsof considerable flexibility so t at. a break in the conductor, or windpressure, will not set up undue stresses. This type of construction alsomakes it possible to place the power conductors quite close together,thereby cutting down the reactance and increasing the amount of powerwhich may be transmitted over the circuit. Any number of conductors maybe supported within reasonable mechanical limitations.

A slightly different type of construction is shown in Fig. 9. In thisinstance, the power conductors 60 are supported by insulators 61, whichin turn are suspended from a cable 62 which is attached to the tops ofmast-s or poles 63. Charging wires 64 are used to prevent burning o thepoles and to function in other ways as previously described. Thecharging wires 64 may be utilized to brace or strengthen the supportslongitudinally of the line. W'here it is necessary to guy the structurewith members 65, it is necessary to insert insulators 66 in order thatthe charging wire may become effective. This makes it possible toutilize the insulation in the poles 63.

Fig. 10 shows a slightly different construction 1n which the powerconductors 70 are supported by insulators 71, which in turn aresupported by a truss member 72, truss rods 73 forming a bond between theupper. ends of the insulators 71. The charging wires74 are connected tothe truss member 73. The insulation of the pole is preferably noteliminated or reduced. The method of applying a ground wire 75 is shown,which makes this possible. The ground wire is located below the powerconduct-or at such a distance that the separation between the powerconductor 70 and the ground wire 75,

will provide the desired insulation. Where ample insulation exists, ajumper T 6 may extend from the chargin wire to the point of attachmentof the insulators 77. Wher the round wire is installed at 78 and agroundmg lead 79 is carried down on the pole, the jumper 76 must, ofnecessity, be omitted.

I claim:

1. In combination a support having a portion thereof insulated fromground, a transmission line mounted on said portion and insulatedtherefrom, a charging line electri cally connected with said portion andgrounded at a distance from said support and an insulated ground wiremounted on said support adjacent said transmission line.

In combination a support having a metallic portion insulated fromground, a transmission line mounted adjacent said metallic portion butinsulated therefrom, a charging line electrically connected with saidmetallic portion and extending through the same region as saidtransmission line for charging said metallic portion similarly tocharges resulting in said transmission line from external disturbancesand for dissipating said charges concurrently with the dissipation ofthe charges from said line and a ground line mounted adjacent saidtransmission line and insulated from said support and transmission linebut connected to ground adjacent said support.'

3. In combination a support having a metallic portion insulated fromground, a transmission line mounted. on said metallic portion butinsulated therefrom, a charging conductor electrically connected withsaid nictallic portion and extending through the same region as saidtransmission line and acting to reduce bound charges on saidtransmission line and to submit the insulated portion of said support tosimilar charges as said transmission line, said charging conductor beingconnected through an overload cut-out to ground at a distance from saidsupport.

4. In combination, a support having a metallic portion insulated fromground, a transmission line mounted on said metallic portion butinsulated therefrom, a charging conductor electrically connected withsaid metallic portion and extending through the same region as saidtransmission line and acting to reduce bound charges on said transmission line and to submit the insulated portion of said support tosimilar charges as said transmission line, said charging conductor beingconnected through a relay to ground at a distance from said support.

5. The combination of a support having a conductor section insulatedfrom ground, a transmission line mounted on said insulated section andinsulated therefrom, a charging conductor electrically connected withsaid insulated section for reducing bound charges in said transm ssionline and for charging the insulated section of said support, saidcharging conductor being connected to ground through a conductorsubjected to coiulitions suitable to give approximately the same rate ofdissipation of charge from the insulated portion of said transmissionline adjacent said support, and a ground wire mounted on the support andinsulated from the support and transmission line and connected to groundadjacent said support for'increasing the electrostatic capacity toground of said transmission line.

6. The combination of a wood support having metallic members mountedthereon and insulated by said support from ground, a transmission linemounted on said support adjacent said metallic members and insulatedtherefrom, a charging conductor electrically connected with saidmetallic members and having connection to ground subject to conditionssuitable to give approximately the same rate of dissipation of chargesfrom said metallic members as from the portion of said transmissionline. adjacent thereto, and a grounded conductor adjacent said transmission line for cooperating with charging conductor to decrease boundcharges on said transmission line and to increase the electrostaticcapacity to ground of said transmission line.

7. In a transmission line system a supporting structure having a woodencross arm, a line conductor and means for supporting the same includinga metallic bolt carried by said cross arm, an arcing horn detachablyconnected to said bolt and a second arcing horn supported on saidstructure and connected to ground and in spaced relation to said firstnamed horn, the adjacentportions of said horns being spaced apart sothat the insulating value of the air gap separating the same is lessthan that of said supporting structure.

8. In a supporting structure for transmis sion lines including a Woodencross arm, a

string of insulators mounted thereon by means of a metallic connectorand arcing horn adapted to be detachably connected to one end of saidmetallic connector, a brace for said cross arm connected to ground andanother arcing horn electrically connected to said brace and spaced fromsaid first named born.

9. In atransmission line system a supporting structure having a woodencross arm, a. line conductor and means for supporting the same includinga metallic member carried by said cross arm, an arcing horn electricallyconnected to 1 said metallic member, and a second arcingihornelectrically connected to ground and in. spaced relation to saidfirstnamed horn, the adjacent portions of said horns being spaced apartso that the insulating value of the air gap separating the same is lessthan that said supporting structure.

10. In a transmission line system, a supporting structure having awooden cross arm, atransmission line and means for supporting thetransmission line including a metallic member carried by said cross arm,an arcing horn electrically connected to said metallic member, a secondarcing horn supported on said structure and electrically connected toground and in spaced? relation to said firstnamed horn,the'adjacentportions of said horns being spaced apart so thatthe'insu'latmg value of the air gap separating the same is less thanthat of the supporting structure separating the two horns, and acharging wire electrically connected with said metallic member.

In testimony whereof I have signed my name to this specification on this21st day of May, A. D. 1927.

ARTHUR O. AUSTIN.

